Despite being a well-known monument, the Roman amphitheatre of Tarragona, which is included in the UNESCO World Heritage List, was only fully studied in the late 1980s. The study was therefore subject to the archaeological research limitations and specific characteristics of that time, as can be seen in the quality of the site's planimetry. The general planimetry was basically available for relevant sections at a scale of 1:100 with sufficient accuracy. However, according to current scientific parameters, this planimetry is clearly inadequate, and cannot be used rigorously to obtain comprehensive architectural knowledge. The technical limitations of the time, and the innate difficulties presented by the monument, meant that only a few sections were obtained, specifically two, with a low level of detail. This has led to misinterpretations, and consequently to dubious or erroneous conclusions. Therefore, the need for complete metric documentation is evident, as this will enable us to correctly analyse the monument. We have obtained metric documentation by carrying out a topographic survey using digital photogrammetry, which provides us with more information than merely measurements. We can use the three-dimensional model that was generated to analyse the sections of the stands and draw conclusions about their geometry.